Abstract:

A series of triaxial shear tests on intact unsaturated Q2 loess were conducted using computerized tomography (CT)-multi-function triaxial apparatus developed in Logistical Engineering University. The distinct CT images and detailed CT data of the evolution of meso-structure were obtained during loading. A new method is proposed to identify the yield stress of intact Q2 loess using curves of CT-number versus deviatoric stress. A structure parameter and a structure evolution variable are defined based on CT data. The variable of structure evolution increases with the increase in net confining pressure under the same suction; while the variable of structure evolution decreases with the increase in suction under the same net confining pressure. An equation describing the evolution of structure is developed. In the equation, deviatoric strain and volumetric strain are included. The equation reflects the influences of net confining pressure and suction on the evolution of meso-structure during loading. The structure evolution equation successfully simulates the laboratory tests of unsaturated intact Q2 loess.

Key words: intact Q2 loess, triaxial shear, computerized tomography (CT), meso-structure, structure parameter, structure evolution equation